Laser light source device, illumination device, image display device, and monitor device

ABSTRACT

A laser light source device includes: a light source; an external resonator, a wavelength conversion element converting the wavelength of part of incident light having the first wavelength into the second wavelength which is different from the first wavelength; and an optical-path conversion element causing the light that has been converted into light of the second wavelength in the process of traveling to the light source due to reflection from the external resonator to be separated into a second optical-path different from the first optical-path, and emitting a second laser light of the second wavelength. In the laser light source device, and the height of the wavelength conversion element is greater than a distance between an optical-axis of the first laser light on an end face of the wavelength conversion element which is close to the external resonator and an optical-axis of the second laser light.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims priority from Japanese PatentApplication No. 2007-004573, filed on Jan. 12, 2007, and Japanese PatentApplication No. 2007-328968, filed on Dec. 20, 2007, the contents ofwhich are incorporated herein by reference.

BACKGROUND

1. Technical Field

The present invention relates to a laser light source device, anillumination device, an image display device, and a monitor device.

2. Related Art

In recent years, in the field of opto-electronics including fiber-opticcommunication, light application measurement, light display, and thelike, laser light source devices have been widely used.

As examples of laser light source devices, laser light source devices inwhich the wavelength of the fundamental wave laser is used directlywithout conversion, and laser light source devices in which a convertedwavelength of the fundamental wave laser is used, are both well-known.

In the laser light source device in which the converted wavelength ofthe fundamental wave laser is used, a wavelength conversion element thatconverts the wavelength of the fundamental wave laser is well-known.

The wavelength conversion element is also called the Second HarmonicGeneration element (SHG element).

Conventionally, since the wavelength conversion efficiency of the SHGelement is approximately 30 to 40%, the power of the light that has beenconverted by the SHG element is appreciably low when compared with thepower of the output light of the fundamental laser light source.

As a constitution suppressing power reduction of the output light, thelaser light source device disclosed in Japanese Unexamined PatentApplication, First Publication No. S59-128525 has been suggested.

In the laser light source device, the light that has been emitted froman internal-resonator type laser light source and has passed through anSHG element is separated into an SHG light whose wavelength has beenconverted and into the residual fundamental-wave light In addition, byleading the residual fundamental-wave light to re-pass through the SHGelement, the second SHG light whose wavelength has been converted isextracted.

The second SHG light is synthesized to a first SHG light in the statemat the second SHG light whose polarization has been converted into thepolarization different from the polarization direction of the first SHGlight by 90°.

In the laser light source device of Japanese Unexamined PatentApplication, First Publication No. S59-128525, in the above-describedmanner, power reduction of the output light is suppressed due toutilization of the light synthesized by both the first SHG light and thesecond SHG light as output light.

In the above-described laser light source device disclosed as JapaneseUnexamined Patent Application, First Publication No. S59-128525, thoughthe second SHG light whose wavelength has been converted by leading theresidual fundamental-wave light to re-pass through the SHG element canbe utilized, the residual fundamental-wave light whose wavelength hasnot been converted even by re-passing through the SHG element can not beutilized. Therefore, light utilization efficiency is never dramaticallyimproved.

In addition, when making the above residual fundamental-wave lightdirectly return to the fundamental laser light source, there is concernthat the power of the fundamental laser light source may be reduced orunstable. Therefore, the constitution making the residualfundamental-wave light not return to the light source is necessary.There is thereby concern that an optical system will increase in size.In addition, there is concern that as the length of the optical-path isextended, and light loss occurs due to an increase in the number oftimes the light passes through the optical elements.

Furthermore, in the above-described laser light source device disclosedas Japanese Unexamined Patent Application, First Publication No.S59-128525, in order to synthesize the first SHG light and the secondSHG light, their polarization directions are made to differ from eachother by 90°, the output light thereby becomes light synthesized by thetwo-type polarization.

Therefore, when the laser light source device disclosed as JapaneseUnexamined Patent Application, First Publication No. S59-128525 is usedin combination with a polarization-controller-type device (e.g., liquidcrystal device) in which only one polarization is utilized, only one SHGlight is allowed to be used in the absence of the constitution in whichthe polarization directions of the first SHG light and the second SHGlight are completed.

That is, in the laser light source device disclosed as JapaneseUnexamined Patent Application, First Publication No. S59-128525, thoughstabilized output can be obtained while suppressing power reduction ofthe output light to some extent, light utilization efficiency in notfurther improved.

Specifically, when used in combination with thepolarization-controller-type device, there is also concern that thelight utilization efficiency is insufficient.

Furthermore, when using the above-described laser light source device incombination with a liquid crystal device, a diffusion optical memberwhich diffuses the light of the laser light source device is necessary.

In addition, since the light which is emitted toward a liquid crystaldevice through a large-size diffusion optical member degrades the imagequality, reducing the size of the diffusion optical member is therebydesired.

SUMMARY

An advantage of some aspects of the invention is to provide a laserlight source device, an illumination device, an image display device,and a monitor device where power reduction of the output light isefficiently suppressed, the light utilization efficiency is improved,stabilized output is obtained due to the polarization direction of theoutput light being completed, and it is possible to reduce the size of adiffusion optical member.

A first aspect of the invention provides a laser light source deviceincluding: a light source emitting light of a first wavelength; anexternal resonator selectively reflecting the light of the firstwavelength and thereby leading the light toward the light source, andemitting a first laser light of a second wavelength which is differentfrom the first wavelength; a wavelength conversion element provided in afirst optical-path formed between the light source and the externalresonator, and converting the wavelength of part of incident lighthaving the first wavelength into the second wavelength which isdifferent from the first wavelength; and an optical-path conversionelement causing the light that has been converted into light of thesecond wavelength in the process of traveling to the light source due toreflection from the external resonator to be separated into a secondoptical-path different from the first optical-path, and emitting asecond laser light of the second wavelength. In the laser light sourcedevice, the first laser light and the second laser light are utilized asoutput lights, and the height of the wavelength conversion element isgreater than a distance between an optical-axis of the first laser lighton an end face of the wavelength conversion element which is close tothe external resonator and an optical-axis of the second laser light.

In other words, when the height of the wavelength conversion element(length of the wavelength conversion element in a direction orthogonalto the optical axis of light passing through the wavelength conversionelement) is W1, and when the distance between the optical-axis of thefirst laser light on the end face of the wavelength conversion elementwhich is close to the external resonator is W2 and the optical-axis ofthe second laser light, the relationship W2<W1 is consistent.

According to the laser light source device of the first aspect of theinvention, the wavelength conversion element is provided in theresonator structure (first optical-path) constituted by the light sourceand the external resonator. In addition, the second laser light whosewavelength has been converted in the process of traveling to the lightsource due to reflection from the external resonator is extracted intothe second optical-path by the optical-path conversion element and isutilized. It is thereby possible to efficiently reduce the powerreduction of the output light.

Furthermore, since the wavelength conversion element is provided insidethe resonator structure constituted by the light source and the externalresonator, a structure is not necessary to lead the light so that thelight does not return to the light source, the light having not beenconverted into a light of the second wavelength while traveling to thelight source due to the reflection from the external resonator.

It is possible to decrease the light loss caused by malfunctions, suchas, by extending the length of the optical-path by increasing the sizeof the optical system or by increasing the number of times the lightpasses through the optical elements.

Furthermore, since it is sufficient that only the direction of thesecond laser light is substantially led to travel in the same directionof travel of the first laser light, it is possible to obtain the outputlight having a substantially completed polarization direction.Therefore, even if, for example, the laser light source device is usedin combination with the polarization-controller-type device, it ispossible to improve light utilization efficiency.

Furthermore, since the relationship W2<W1 is satisfied, the distancebetween the second laser light and the first laser light is narrowed.Therefore, for example, when a diffusion optical member is located inadvance of the two laser lights, it is possible to reduce the size ofthe diffusion optical member.

The light that is emitted through the diffusion optical member whosesize is reduced can obtain clean illumination with a high level of imagequality and a high level of light utilization efficiency.

Furthermore, according to the laser light source device of the firstaspect of the invention, even if the bottom portion of the light source,the external resonator, the wavelength conversion element, and theoptical-path conversion element are held by a fixing member, such as, anadhesive, a mechanical clamp, or the like, since the above-describedrelationship (W2<W1) is satisfied, interception of the first and secondlaser lights by the fixing member does not occur. Therefore, reductionof yield can be prevented.

Furthermore, since the laser beam can be incident into the substantiallysame portion of a diffusion member and can be reliably obtained theillumination onto the substantially same region, it is possible torealize a high level of illumination efficiency while reducing lightloss.

Therefore, it is possible to reduce the size of the diffusion opticalmember, which is used in combination with the laser light source device.In addition, the laser light source device having a high level of lightutilization efficiency and emitting the output light having asubstantially completed polarization direction is realized, and in whichthe output is stabilized, while efficiently suppressing power reductionof the output light.

It is preferable that, in the laser light source device of the firstaspect of the invention, the height of the external resonator be greaterthan the distance between the optical-axis of the first laser light andthe optical-axis of the second laser light.

In other words, when the height of the external resonator (length of theexternal resonator in a direction orthogonal to the first laser lightpassing through the external resonator) is W3, it is preferable that therelationship W2<W3 be consistent.

In this constitution, since the relationship W2<W3 is satisfied inaddition to the above-described relationship (W2<W1), it is possible toavoid a reduction in the transmissivity of the optical member that isdisposed in the optical-path, caused by the effect of, for example, anadhesive or a holding member which holds the bottom side portion of theexternal resonator. It is thereby possible to further improve lightutilization efficiency.

In addition, the external resonator needs to align the reflection faceof the external resonator with the light source, based on the length inthe direction of a beam and the reflection angle. However, according tothe invention, it is easy to fix the external resonator and the lightsource at a desired angle while easily aligning the external resonatorand the light source, and it is possible to prevent interception of thesecond laser light.

It is preferable that, in the laser light source device of the firstaspect of the invention, the first laser light be substantially parallelto the second laser light.

There is a high possibility that the laser light source device will beused in combination with other optical devices such as lenses, filters,mirrors, diffraction gratings, prisms, light modulation elements, andthe like. The characteristics of these optical devices may varydepending on the angle of the incidence light.

Furthermore, illumination loss occurs for obtaining margin inirregularities of illumination region, caused by irregularities of theangles of the incidence light.

By adopting the invention, since the first laser light is substantiallyparallel to the second laser light, it is easy to design an opticaldevice or to determine the position of an optical device, which isdisposed behind the laser light source device.

Therefore, more specifically, when the laser light source device isapplied to an image display device, a monitor device, or the like, it ispossible to obtain effects where the degree of freedom in optical designincreases dramatically.

Furthermore, since the illumination region which is obtained in advanceof the diffusion optical member is formed on the region depending on theincidence angle of the laser beam, it is possible to illuminate thesubstantially same region, and it is possible to illuminate a desiredarea with a high level of illumination efficiency.

It is preferable that, in the laser light source device of the firstaspect of the invention, the length of the optical-path conversionelement in the direction of the beam of the second laser light emittedfrom the optical-path conversion element be shorter than the height ofthe optical-path conversion element.

In other words, when the length of the optical-path conversion element(the length of the optical-path conversion element in the direction ofthe beam of the second laser light which is emitted from theoptical-path conversion element) is W4, and when the height of theoptical-path conversion element (the length of the optical-pathconversion element in a direction orthogonal to the optical axis oflight passing through the wavelength conversion element) is W5, it ispreferable that the relationship W4<W5 be consistent.

By this constitution, the size of the optical-path conversion element inthe direction of the beam of the second laser light is suppressed, thesize of the wavelength conversion element is enlarged as much aspossible, and the length of the wavelength conversion optical-path inthe wavelength conversion element can be reliably elongated.

Therefore, the conversion efficiency that a wavelength is converted intothe second wavelength in the wavelength conversion element is improved,and it is possible to further improve the light utilization efficiency.

A second aspect of the invention provides a laser light source deviceincluding: a light source emitting light of a first wavelength; anexternal resonator selectively reflecting the light of the firstwavelength and thereby leading the light toward the light source, andemitting a first laser light of a second wavelength which is differentfrom the first wavelength; a wavelength conversion element provided in afirst optical-path formed between the light source and the externalresonator, converting the wavelength of part of incident light havingthe first wavelength into the second wavelength which is different fromthe first wavelength, and thereby obtaining harmonics; an optical-pathconversion element causing the light that has been converted into lightof the second wavelength in the process of traveling to the light sourcedue to reflection from the external resonator to be separated into asecond optical-path different from the first optical-path, and emittinga second laser light of the second wavelength; and an optical-pathadjustment section adjusting the first laser light to be output from apredetermined position in the wavelength conversion element. In thelaser light source device, the first laser light and the second laserlight are utilized as output lights.

In the laser light source device of the second aspect of the invention,the wavelength conversion element is provided in the resonator structure(first optical-path) constituted by the light source and the externalresonator. In addition, the second laser light whose wavelength has beenconverted in the process of traveling to the light source due toreflection from the external resonator is extracted into the secondoptical-path by the optical-path conversion element and is utilized. Itis thereby possible to efficiently reduce the power reduction of theoutput light.

Furthermore, since the wavelength conversion element is provided insidethe resonator structure constituted by the light source and the externalresonator, a structure is not necessary to lead a light so that thelight does not return to the light source, the light having not beenconverted into a light of the second wavelength while traveling to thelight source due to the reflection from the external resonator.

It is possible to decrease the light loss caused by malfunctions, suchas, by extending the length of the optical-path by increasing the sizeof the optical system or by increasing the number of times the lightpasses through the optical elements.

Furthermore, since it is sufficient that only the direction of thesecond laser light is substantially led to the same direction of travelof the first laser light it is possible to obtain the output lighthaving a substantially completed polarization direction. Therefore, evenif, for example, the laser light source device is used in combinationwith the polarization-controller-type device, it is possible to improvelight utilization efficiency.

Furthermore, the distance between the second laser light and the firstlaser light can be narrowed by the optical-path adjustment section.When, for example, a diffusion optical member is located in advance ofthe two laser lights, it is possible to reduce the size of the diffusionoptical member.

The light that is emitted through the diffusion optical member whosesize is reduced can obtain clean illumination with a high level of imagequality and a high level of light utilization efficiency.

Furthermore, by the optical-path adjustment section, it is possible tolead the light of first wavelength making the first laser light passthrough a predetermined position (for example, a portion in which thepitch of polarization inversion is stabilized in the wavelengthconversion element) in the wavelength conversion element. It is therebypossible to improve the reliability.

Therefore, it is possible to reduce the size of the diffusion opticalmember, which is used in combination with the laser light source device.The laser light source device having a high level of light utilizationefficiency is realized, in which polarization directions of the outputlight is completed, and the output is stabilized, while efficientlysuppressing power reduction of the output light.

It is preferable that, in the laser light source device of the secondaspect of the invention, the optical-path conversion element include: afundamental-wave conversion section converting the optical-path of thelight of the first wavelength from the light source; a separationsection selectively reflecting the light that has been converted intothe second wavelength in the process of traveling to the light sourcedue to reflection from the external resonator and thereby separating thelight into the second optical-path; and a harmonics optical-pathconversion section converting the optical-path of light of the secondwavelength that has been separated by the separation section and therebymaking the light become the second laser light.

By using the optical-path conversion element it is possible to reliablyobtain the above-described first laser light and second laser light.

It is preferable that, in the laser light source device of the secondaspect of the invention, the optical-path conversion element include theoptical-path adjustment section.

In this constitution, since the optical-path adjustment section isconstituted by a part of the optical-path conversion element, it ispossible to simplify the constitution of the laser light source device.

It is preferable that in the laser light source device of the secondaspect of the invention, the optical-path adjustment section beconstituted by a support member supporting the optical-path conversionelement.

In this constitution, the optical-path conversion element can be heldonto a predetermined position, and as described above, it is therebypossible to reliably extract the second laser light toward an exterior.

It is preferable that in the laser light source device of the first andthe second aspect of the invention, the wavelength conversion elementinclude a holding face onto which a face of the wavelength conversionelement is held, and a center section parallel to the optical-path ofthe first laser light in the wavelength conversion element. In the laserlight source device, the optical-path of the first laser light ispositioned inside the wavelength conversion element and between thecenter section and the optical-path of the second laser light.

In this constitution, it is possible to lead the first laser light to beclose to the second laser light while leading the first laser light topass through the inner wavelength conversion, element and the secondlaser light to pass outside the wavelength conversion element.

It is preferable that, in the laser light source device of the first andthe second aspect of the invention, the light source include a pluralityof arrayed emission sections.

In the invention, when the arrayed light source is used, the area of theemission end face (the incident end face) of the optical-path conversionelement, the wavelength selective element, and the external resonator,can be suitably expanded depending on the area of the array.

Therefore, in the above-described constitution, even if the light sourceis an array, the device does not need to be extremely increased in size,and it is possible to utilize the simple constitution described above.

Therefore, even if the light source is an array, it is possible toefficiently improve the output power of the output light by increasingthe amount of light by arraying, while obtaining the effects in whichpower reduction of the output light can be efficiently suppressed, lightutilization efficiency can be improved, the output light has asubstantially completed polarization direction, and the output can bestabilized.

It is preferable that, in the laser light source device of the first andthe second aspect of the invention, the wavelength conversion element bea wavelength conversion element of Quasi Phase Matching.

In this constitution, since the wavelength conversion element of theQuasi Phase Matching whose conversion efficiency is higher than that ofother types of wavelength conversion elements is included, the degree ofeffectiveness of the invention is further improved.

A third aspect of the invention provides an illumination deviceincluding: the laser light source device described above; and adiffusion optical member arranged in the direction of travel of thelaser light emitted from the laser light source device.

According to the illumination device of the third aspect of theinvention, since the above-described laser light source device isincluded, reduction of the size of the diffusion optical member isachieved, and the illumination device having high performance can berealized into the reduced size with a high level of image quality oflight.

It is preferable that, in the illumination device of the third aspect ofthe invention, the diffusion optical member be formed by a computergenerated hologram.

In this constitution, the size of the computer generated hologram isreduced, and it is possible to further improve the light utilizationefficiency.

A fourth aspect of the invention provides an image display deviceincluding: a light source section constituted by the illumination devicedescribed above; and a light modulation element modulating the lightemitted from the light source in accordance with image information.

According to the image display device of the fourth aspect of theinvention, since the illumination device having the above-describedlaser light source device is included as the light source, a high levelof light utilization efficiency is obtained.

A fifth aspect of the invention provides a monitor device including: thelaser light source device described above; a capturing section capturingan object which is irradiated by the laser light source device.

According to the monitor device of the fifth aspect of the invention,since the above-described laser light source device is included, a highlevel of light utilization efficiency is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a constitution of a laser lightsource device of a first embodiment.

FIG. 2 is a schematic cross-sectional view of a constitution of a lightsource.

FIG. 3 is a schematic cross-sectional view showing a constitution of awavelength conversion element.

FIG. 4 is a schematic cross-sectional view showing a constitution of anexternal resonator.

FIG. 5 is a perspective view of an optical-path conversion element.

FIG. 6 is a schematic view of a constitution of a laser light sourcedevice of a second embodiment.

FIGS. 7A and 7B are schematic perspective views showing a constitutionof light source having a plurality of arrayed emission sections.

FIG. 8 is a schematic cross-sectional view showing a constitution of anexternal resonator of a modified example.

FIG. 9 is a schematic perspective view showing a constitution of anillumination device.

FIG. 10 is a schematic view showing a constitution of an optical systemof a projector.

FIG. 11 is a schematic view showing a constitution of a monitor device.

FIGS. 12A and 12B are schematic views showing constitutions of laserlight source devices of a third embodiment, FIG. 12A is a side view ofthe laser light source device, and FIG. 12B is a cross-sectional viewillustrating the optical-path in the laser light source device.

FIG. 13 is a cross-sectional view illustrating the positionalrelationship between a reflection surface of a prism and a wavelengthconversion element.

FIG. 14 is a schematic view showing a constitution of a laser lightsource device of a fourth embodiment.

FIG. 15 is a schematic view showing a constitution of a laser lightsource device of a fifth embodiment.

FIG. 16 is a schematic view showing a constitution of a laser lightsource device of a modified example.

FIG. 17 is a schematic view showing a constitution of a laser lightsource device of a modified example.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, the invention will be described with reference to theaccompanying drawings.

The scale of each member in the drawings below has been changedappropriately to sizes that enable each member to be recognized easily.

First Embodiment

FIG. 1 is a schematic view showing a constitution of a laser lightsource device of the first embodiment.

A laser light source device 31 includes a light source 311, a wavelengthconversion element 312 (Harmonic Generation element), an externalresonator 313, and an optical-path conversion element 314.

The light source 311 emits light of a first wavelength.

In the laser light source device 31 of the first embodiment the lightsource 311, the wavelength conversion element 312, the externalresonator 313, and the optical-path conversion element 314 is held ontoa base section B constituted by, for example, a metal frame or the like.

The constituting members of the laser light source device 31 (the lightsource 311, the wavelength conversion element 312, the externalresonator 313, the optical-path conversion element 314) are fixed on thebase section B (fixing member) by adhesive C.

As the method for constituting each of the members, the combination thebase section B with the adhesive is not limited, for example, amechanical clamp or the like may be adopted.

FIG. 2 is a schematic cross-sectional view showing the structure of thelight source 311.

As shown in FIG. 2, the light source 311 emitting laser light isreferred to as a surface emission-type semiconductor laser. The lightsource 311 includes, for example, a substrate 400 constituted by asemiconductor wafer, a mirror layer 311A formed on the substrate 400 andfunctioning as a reflection mirror, and a laser medium 311B laminated onthe top surface of the mirror layer 311A.

The mirror layer 311A is constituted by a lamination body including adielectric having a high refractive index and a dielectric having a lowrefractive index. These dielectrics are formed on the substrate 400 by,for example, a CVD (Chemical Vapor Deposition) method.

The thickness of each layer instituting the mirror layer 311A, thematerial of each layer, and number of the layers are optimized dependingon the wavelength (first wavelength) of the light emitted from the lightsource 311. The structure of the mirror layer 311A is optimized so thata high level of light intensity is obtained through interference withand amplification by the reflected light.

The laser medium 311B is formed on the surface of the mirror layer 311A.An electriferous section (not shown) is connected with the laser medium311B. The laser medium 311B emits a laser light having a wavelengthpredetermined by the amount of current applied by the electriferoussection.

The laser medium 311B causes the light including the specific wavelength(first wavelength) to be amplified by resonation the light of the firstwavelength between the mirror layer 311A and the external resonator 313as shown in FIG. 1.

Therefore, the light reflected by the mirror layer 311A and the externalresonator 313 described below is amplified by resonation with the lightnewly emitted from the laser medium 311B. By this constitution, thelight which has been resonated is emitted from the light emission endface of the laser medium 311B in a direction substantially orthogonal tothe substrate 400 or the mirror layer 311A.

The wavelength conversion element 312 converts the wavelength of thelight which is incident into itself into the substantial half wavelength(second wavelength) of the light.

As shown in FIG. 1, the wavelength conversion element 312 is provided ina first optical-path O1 formed between the light source 311 and theexternal resonator 313.

Furthermore, the wavelength conversion element 312 includes a centersection (center line) which is parallel to the first optical-path O1 ofthe inner wavelength conversion element 312.

In addition, the wavelength conversion element 312 includes a holdingface 312D. On the holding face 312D, the wavelength conversion element312 is held onto the base section B.

FIG. 3 is a schematic cross-sectional view showing the structure of awavelength conversion element 312.

The wavelength conversion element 312 is formed, for example, in aquadrangular pillar-shaped form, and includes a wavelength conversionsection 312A and anti-reflective films (AR films) 312B and 312C.

The anti-reflective film 312B is formed on the surface (incidence endface) of wavelength conversion section 312A which is close to the lightsource 311.

The anti-reflective film 312C is formed on the surface (emission endface) of the wavelength conversion section 312A which is closer to theexternal resonator 313.

The wavelength conversion section 312A is a Second Harmonic Generationelement (SHG element) generating second harmonics of the light which isincident into itself.

The wavelength conversion section 312A includes a periodic polarizationinversion structure. In the wavelength conversion section 312A, thewavelength of the light which is incident into itself is converted intothe substantial half wavelength (second wavelength) of the light due tothe wavelength conversion by Quasi Phase Matching (QPM).

In this manner, since the Quasi Phase Matching whose conversionefficiency is higher than that of other types of wavelength conversionelements is used, the degree of effectiveness of the invention asdescribed below is further improved.

For example, when the wavelength (first wavelength) of the light emittedfrom the light source 311 is 1064 nm (near infrared), the wavelengthconversion section 312A converts the first wavelength into a wavelengthhalf as large, which is 532 nm (the second wavelength). The wavelengthconversion section 312A thereby generates a green-colored light.

However, as described above, the conventional wavelength conversionefficiency of the wavelength conversion section 312A is approximately 30to 40%. Thus, all light emitted from the light source 311 is notconverted into the second wavelength light.

The periodic polarization inversion structure is formed in a crystalsubstrate made of an inorganic nonlinear optical material (e.g., lithiumniobate (LiN:LiNbO₃), lithium tantalate (LT:LiTaO₃), or the like).

Specifically, in the periodic polarization inversion structure, aplurality of two types regions 312Aa and 312Ab whose polarizationdirections are inverted to each other are formed. The regions 312Aa and312Ab are alternately formed by a predetermined distance in a directionsubstantially orthogonal to the emission direction of the light emittedfrom the light source 311.

The pitch between the two regions 312Aa and 312Ab are determined by thewavelength of the incidence light and the refractive-index dispersion ofthe crystal substrate, as needed.

Conventionally, in the laser light oscillated from a semiconductorlaser, a plurality of longitudinal modes oscillates in gain-bandwidth,and the wavelength thereof is varied by temperature change or the like.

Therefore, the allowable range of the wavelength of the light which isconverted in the wavelength conversion element 312, is approximately 0.3nm. The allowable range varies at approximately 0.1 nm/° C. depending onthe temperature of service condition.

The AR films 312B and 312C are, for example, dielectric filmsconstituted by a single layer or a multilayer, and lead both the firstwavelength light and the second wavelength light to pass therethrough,for example, at a transmissivity greater than or equal to 98%.

These AR films 312B and 312C may be omitted because the AR films 312Band 312C are not essential films for achieving functions of thewavelength conversion element 312.

Thus, the wavelength conversion element 312 can be constituted by thewavelength conversion section 312A alone.

The external resonator 313 has functions so that the light of the firstwavelength is led to selectively reflect toward the light source 311,and so that the light other that of the first wavelength and the lightincluding the second wavelength is led to pass through.

The external resonator 313 also has the function to narrow the bandwidthof the wavelength of the light which is amplified by selectivelyreflecting the light of the first wavelength.

As shown in FIG. 1, the external resonator 313 is formed on the firstoptical-path O1 so as to be disposed substantially orthogonal to thefirst optical-path O1.

Furthermore, the incidence end face of the external resonator 313 facestoward the emission end face of the wavelength conversion element 312.

FIG. 4 is a schematic cross-sectional view showing the structure of theexternal resonator.

The external resonator 313 is formed in a quadrangular pillar-shapedform similar to the wavelength conversion element 312.

The external resonator 313 also includes a Bragg grating section 313Athat is the volume phase grating in which a Bragg grating structure isformed, and an anti-reflective film 313B (AR film) that is formed on thesurface (incidence end face) of the Bragg grating section 313A, which iscloser to the wavelength conversion element 312.

The Bragg grating section 313A is constituted by a plurality of layersformed along the optical-path O1.

The Bragg grating section 313A is formed in a glass layer so as tolaminate the interference patterns having different refractive indexeseach other, by irradiating with ultraviolet light having a predeterminedwavelength onto the glass layer constituting a material mainly includingSiO₂, such as alkali boro-aluminosilicate glass or the like.

Due to the Bragg grating section 313A, the functions of the externalresonator 313 described above can be obtained.

The AR film 313B is a dielectric film constituted by a single layer or amultilayer and leads both the first wavelength light and the secondwavelength light to pass therethrough, for example, at a transmissivitygreater than or equal to 98%.

The AR film 313B can be formed not only at the incidence end face of theBragg grating section 313A but also at the emission end face.

The AR film 313B may be omitted because the AR film 313B is not anessential film for achieving the functions of the external resonator313.

Thus, the external resonator 313 can be constituted by the Bragg gratingsection 313A alone.

FIG. 5 is a perspective view showing an optical-path conversion element314.

As shown in FIGS. 1 and 5, the optical-path conversion element 314includes first and second prisms 315 and 316 which are translucentmembers, and a selective reflection film 317 formed between the firstand second prisms 315 and 316.

The prism 315 is made of an optical glass such as BK7 or the like, in anisosceles triangular pillar-shaped form. As shown in FIG. 1, a surface315A of the prism 315 is disposed so as to face the light source 311. Inaddition, the surface 315A is disposed so as to be substantiallyorthogonal to the first optical-path O1.

Furthermore, a surface 315B is parallel to a surface 316B of the secondprism 316 described below. In addition, a surface 315C is a flat surfacewhich is disposed at the angle so that the total reflection conditionrelative to the first optical-path O1 is obtained.

That is, the surfaces 315C and 315B of the first prism function as afundamental-wave conversion section which changes the optical-path inthe light of the first wavelength from the light source 311 and leadsthe light toward the second prism 316.

The second prism 316 is made of an optical glass such as BK7 or the likesimilar to the first prism 315, in a triangular pillar-shaped form.

Three side surfaces of the prism 316 are constituted by surfaces 316Band 316C which include two sides sandwiching the vertex angle of thetriangular, and a surface 316A which includes the oblique side.

The selective reflection film 317 is formed on the surface 316B.

The selective reflection film 317 is formed of, for example, adielectric multilayer.

The dielectric multi layer can be formed by, for example, a CVD(Chemical Vapor Deposition) method.

The thickness of each layer constituting the multi layer, the materialof each layer, and the number of layers are optimized depending on therequirements of the characteristics.

The selective reflection film 317 is provided between the light source311 and the wavelength conversion element 312 and has thecharacteristics in that the light having the second wavelength is led toselectively reflect and in that the light having the first wavelength isled to pass therethrough.

That is, the selective reflection film 317 includes the functions of adichroic mirror. Therefore, the surface 316B functions as a separationsection, which selectively reflects the light of the second wavelength,and which thereby separates the light into the second optical-path 02mat is different from the above-described first optical-path O1.

In the selective reflection film 317, it is preferable that thetransmissivity relative to the light of the first wavelength and thereflectance relative to the light including the second wavelength behigh, but it is sufficient that the degree of the transmissivity and thereflectance are greater than 80%.

The surface 315B of the first prism 315 is connected to the surface 316Bof the prism 316 on which the selective reflection film 317 is formed,via an optical adhesive, for example, an adhesive curable by ultravioletlight or the like.

The surface 316A is disposed so as to face toward a part of thewavelength conversion element 312.

In addition, the surface 316A is disposed so as to be substantiallyorthogonal to the first optical-path O1.

The surface 316C is a flat surface which is disposed at the angle sothat the total reflection condition relative to the incidence light IL(reference to FIG. 1) is obtained.

By making the surface 316C be the flat surface which is disposed at theangle at which the total reflection condition relative to the incidencelight IL is obtained, it is possible to increase the reflectionefficiency of the reflection surface to approximately 100%, and theutilization efficiency of the light is further improved.

That is, since the surface 316C of the above-described second prism 316can totally reflect the light of the second wavelength, the surface 316Cfunctions as a harmonics optical-path conversion section which convertsthe optical-path of the light of the second wavelength that wasseparated at the selective reflection film 317.

As the harmonics optical-path conversion section, a reflection film maybe provided on the surface 316C. By the reflection film, the harmonicsoptical-path conversion section may lead the second laser light LS2 totend toward the substantially same direction of travel of the firstlaser light LS1.

In this structure, there is a possibility that the reflection efficiencymay slightly decrease. However, it is not necessity to dispose thesurface 316A at an angle at which the total reflection condition isobtained in this structure. Therefore, the degree of freedom in designthe optical-path increases.

The prisms 315 and 316 are integrated into a unit body by connectingeach other.

The prisms 315 and 316 may be integrated into a unit body by anotherconnection method.

The selective reflection film 317 may also be formed on the surface 315Bof the prism 315 instead of on the surface 316B of the prism 316.

In short, ft is sufficient that the selective reflection film 317 beformed between the surface 315B of the prism 315 and the surface 316B ofthe prism 316.

In addition, an anti-reflective film (AR film) may be formed on thesurface 315A of the prism 315 and the surface 316A of the prism 316.

By forming the AR films on these surfaces, it is possible to decreasethe light loss when the light is incident into the optical-pathconversion element 314 via the AR film or when the light is emitted fromthe optical-path conversion element 314 via the AR film.

Next, the process in which output light is obtained from the laser lightsource device 31 will be described.

The light source 311 emits light of the first wavelength when a currentis applied to the laser medium 311B.

The light of the first wavelength emitted from the light source 311 isincident into the surface 315A of the prism 315. In this manner, thelight is incident into the optical-path conversion element 314. Afterthe light was totally reflected by the surface 315C of the prism 315,the light passes through the surface 315B of the prism 315, passesthrough the selective reflection film 317 and the surface 316B of theprism 316 in sequence, and emits from the surface 316A of the prism 316toward the wavelength conversion element 312.

The light of the first wavelength emitted from the optical-pathconversion element 314 is incident into the wavelength conversionelement 312.

In the wavelength conversion element 312, a part of the incident lightof the first wavelength is converted into a light including a light withthe second wavelength which is half of that of the first wavelength.

In the light emitted from the wavelength conversion element 312, thelight that has a wavelength which has been converted into the secondwavelength passes through the external resonator 313, and emits from theexternal resonator 313 as the first laser light LS1.

Additionally, in the light emitted from the wavelength conversionelement 312, the light (light of the first wavelength) which has notbeen converted into light of the second wavelength is reflected by theexternal resonator 313 toward the light source 311.

The light of the first wavelength which has been reflected by theexternal resonator 313 re-passes through the wavelength conversionelement 312 in the process of traveling to the light source 311. Inaddition, a part of the light is converted into light of the secondwavelength.

The light emitted from the wavelength conversion element 312 toward thelight source 311 is incident into the optical-path conversion element314 via the surface 316A of the prism 316, and is incident into theselective reflection film 317.

In the light which has been incident into the selective reflection film317 in this manner, the light of the first wavelength passes through theselective reflection film 317.

The light of the first wavelength which has passed through the selectivereflection film 317 passes the surface 315B of the prism 315. Aftertotal reflection by the surface 315C of the prism 315, the light isemitted from the surface 315A of the prism 315 toward the light source311.

Furthermore, the light is returned to the light source 311, reflected bythe mirror layer 311A, and re-emitted from the light source 311.

As described above, the light of the first wavelength oscillates on thefirst optical-path O1 formed between the light source 311 and theexternal resonator 313. The light is thereby amplified by resonationwith the light newly oscillated in the laser medium 311B.

That is, the laser light source device 31 includes a resonator structureformed between the mirror layer 311A of the light source 311 and theexternal resonator 313.

The light, which has been converted into light of the second wavelengthby the wavelength conversion element 312 in the process of traveling tothe light source 311, is reflected by the selective reflection film 317.

In addition, the light is reflected by the surface 316C of the prism316, which is a reflective surface, thereby led in a directionsubstantially parallel to the direction of travel of the first laserlight LS1, and emitted from the surface 316A of the prism 316. The lightis the second laser light LS2.

That is, the optical-path conversion element 314 has the functions ofextracting the light, which has been converted into the secondwavelength in the process of traveling to the light source 311 due tothe reflection from the external resonator 313, from the firstoptical-path O1 to the second optical-path O2 which is different fromthe first optical-path O1.

In addition, in the limited cases in which the above-described functionsare achieved, the structure including prisms formed in forms other thanthe above-described first prism 315 and second prism 316 may be used asthe optical-path conversion element 314.

In FIG. 1, L1 indicates the light which has been emitted from the lightsource 311, which has been converted into light of the second wavelengthby the wavelength conversion element 312, and which is emitted from theexternal resonator 313 as the first laser light.

The optical-path O1 indicates the light which has not been convertedinto the second wavelength light by the wavelength conversion element312 after emission from the light source 311, which also has not beenconverted into the second wavelength light by the wavelength conversionelement 312 in the processes from the reflection from the externalresonator 313 toward the light source 311, and which is returned to thelight source 311 by passing the selective reflection film 317.

Furthermore, L2 indicates the light which has been emitted from thelight source 311, has not been converted into the second wavelengthlight by the wavelength conversion element 312, has been converted intothe second wavelength light by the wavelength conversion element 312 inthe processes from the reflection from the external resonator 313 to thereturn to the light source 311, and is incident into the selectivereflection film 317.

In FIG. 1, L1, O1, and L2 appropriately indicate the differentpositions. However, these are referred to actually exist at identicalpositions.

Next, the relationship between the distance between the first laserlight LS1 and the second laser light LS2, and the width of thewavelength conversion element 312 and the external resonator 313 isexplained with reference to the FIG. 1.

In FIG. 1, reference numeral W1 indicates the height of the wavelengthconversion element 312, in other words, indicating the length of thewavelength conversion element 312 in a direction parallel to the line(not shown) orthogonal to the optical-axes (first laser light LS1 andsecond laser light LS2) of lights passing through the inner wavelengthconversion element 312.

Reference numeral W2 indicates the distance between the optical-axis ofthe first laser light LS1 on the end face of the wavelength conversionelement 312 which is close to the external resonator 313 and theoptical-axis of the second laser light LS2.

The laser light source device of this embodiment includes anoptical-path adjustment section. The optical-path adjustment sectionadjusts the optical-path of the light source 311 so as to output thefirst laser light LS1 from a predetermined position of the wavelengthconversion element 312.

In this embodiment, the first prism 315 constituting the optical-pathconversion element 314 includes the optical-path adjustment section.

That is, the optical-path adjustment section constitutes a part of theoptical-path conversion element 314.

As shown in FIG. 1, the first prism 315 includes a foundation section315D (optical-path adjustment section) which causes the surfaces 315Band 315C functioning as the fundamental-wave conversion section to bepositioned at a predetermined height.

In the above-described constitution, in the laser light source device 31of the embodiment, the relationship W2<W1 is satisfied.

Specifically, W1 is 0.5 mm, and W2 is 0.3 mm.

Furthermore, as described above, the first prism 315 (optical-pathconversion element 314) and the wavelength conversion element 312 areheld onto the base section B.

In addition, the first laser light LS1 passes through the innerwavelength conversion element and between the center section CL and theoptical-path of the second laser light LS2.

In other words, the first laser light LS1 passes between the centersection CL of the wavelength conversion element 312 and the top face(face opposite the holding face 312D) of the wavelength conversionelement 312.

In this constitution, it is possible to allow the first laser light LS1to be close to the second laser light LS2, while the optical-path of thefirst laser light LS1 is passing through the inner wavelength conversionelement 312, and while the optical-path of the second laser light LS2 ispassing outside the wavelength conversion element 312.

Furthermore, in FIG. 1, reference numeral W3 indicates the height of theexternal resonator 313, in other words, indicating the length of theexternal resonator 313 in a direction parallel to the line orthogonal tothe first laser light LS1 passing through the external resonator 313.

In the laser light source device 31 of this embodiment, the relationshipW2<W3 is satisfied in addition to the above-described relationship(W2<W1).

In addition, in this embodiment, as shown in FIG. 1, W1<W3 isconsistent.

Specifically, the W3 is 1.2 mm.

Furthermore, in FIG. 1, reference numeral W4 indicates the length of theoptical-path conversion element 314 in the direction of the beam of thesecond laser light LS2 emitted from the optical-path conversion element314.

Reference numeral W5 indicates the height of the optical-path conversionelement 314, in other words, indicating the length of the optical-pathconversion element 314 in a direction parallel to the line orthogonal tothe light axis of the light (laser light LS1) passing through the inneroptical-path conversion element 314.

In the laser light source device 31 of this embodiment, the relationshipW4<W5 is satisfied.

Specifically, the W4 is 7 mm. The W5 is, for example, substantially 10mm.

In conventional laser light source devices, by disposing an externalresonator at the position at which the light emitted from a light sourceis focused, improvement of utilization efficiency of the light isattempted. Therefore, the wavelength conversion element provided betweenthe external resonator and the light source is restricted in size. Byextending the length of the wavelength conversion element through whichthe light passes, that is, by extending the length of the optical-pathin the wavelength conversion element, wavelength conversion efficiencyis improved.

Thus, in laser light source devices, it is desirable that the length ofthe optical-path in the direction of the laser light LS1 and LS2 of thewavelength conversion element be as great as possible.

In contrast, according to the laser light source device 31 of thisembodiment, since the above-described relationship (W4<W5) is satisfiedin the optical-path conversion element 314, the size of optical-pathconversion element 314 is suppressed in the direction of length of theoptical-path of the wavelength conversion element 312. It is therebypossible to enlarge the wavelength conversion element 312 as much aspossible. Furthermore, corresponding to the above, it is possible toreliably obtain elongation of the length of the wavelength conversionoptical-path in the wavelength conversion element 312. The conversionefficiency of light being converted into the second wavelength in thewavelength conversion element 312 is thereby improved, and the lightutilisation efficiency is advanced.

Regarding to a concrete dimension of the laser light source device 31,the width of the wavelength conversion element 312 in a direction oflength of the optical-path is 5 mm.

Furthermore, the length of the optical-path (distance between thesurface of an anti-reflection 313B of the external resonator 313 and thesurface 316A of the optical-path conversion element 314) of the light,which is emitted from the optical-path conversion element 314 andreaches the external resonator 313, is set to 8.5 mm.

In the laser light source device 31 of this embodiment, it is possibleto obtain the effects described below.

(1) Since the wavelength conversion element 312 is provided in theresonator structure (first optical-path O1) constituted by the lightsource 311 and the external resonator 313, it is possible to utilize thesecond laser light by extracting the second laser light which has beenconverted into the second wavelength in the process of traveling to thelight source 311 due to the reflection from the external resonator 313,from the first optical-path O1 to the second optical-path O2, using theoptical-path conversion element 314. It is thereby possible toefficiently prevent power reduction of the output light.

Furthermore, since the wavelength conversion element 312 is provided inthe inner resonator structure constituted by the light source 311 andthe external resonator 313, a structure is not necessary to lead thelight so that the light does not return to the light source 311, thelight having not been converted into a light of the second wavelengthwhile traveling to the light source 311 due to the reflection from theexternal resonator 313.

Thus, there is little concern that the optical system will increase insize, and it is possible to decrease the light loss caused by extendingthe length of the optical-path or by increasing the number of times thelight passes through the optical elements.

Furthermore, since it is sufficient that the second laser light LS2 isled only in substantially the same direction as the direction of travelof the first laser light LS1, it is thereby possible to obtain outputlight in which the polarization directions are almost identical.

It is also thereby possible to improve the light utilization efficiencyeven if the laser light source device is used in combination with apolarization-controller-type device (e.g., liquid crystal device).

(2) As described above, since the optical-path conversion element 314includes the optical-path adjustment section adjusting the optical-pathof the light source 311 so that the first laser light is output from thepredetermined position of the wavelength conversion element 312, it ispossible to obtain a constitution in which the above-describedrelationship W2<W1 is satisfied.

The distance between the second laser light LS2 and the first laserlight LS1 can thereby be shortened.

Furthermore, for example, when a diffusion optical member 50 is locatedin advance of the two laser lights LS1 and LS2, it is possible to reducethe size of the diffusion optical member 50.

Therefore, the light that is emitted through the diffusion opticalmember 50 whose size is reduced can obtain a high level of imagequality, and an illumination device which can obtain clean illuminationwith a high level of light utilization efficiency can be provided.

Furthermore, since the optical-path adjustment section (foundationsection 315D) described above is included, it is possible to lead lightof the first wavelength, and make the first laser light LS1 pass throughthe predetermined position in which the pitch of the polarizationinversion is stabilized in the wavelength conversion element 312, it ispossible to improve the reliability of the laser light source device 31.

Furthermore, according to the invention, even if the bottom side portionof the light source 311, the external resonator 313, the wavelengthconversion element 312, and the optical-path conversion element 314 areconnected to the base section B via the adhesive C, malfunctions, suchas the interception of the optical-path due to the adhesive C, do notoccur, and reduction of the yield caused by the malfunctions can beprevented.

Therefore, it is possible to reduce the size of the diffusion opticalmember 50 which is used in combination with the laser light sourcedevice. In addition, a high level of light utilization efficiency in thelaser light source device 31 can be achieved, in which the output lighthas a completed polarization direction, the output is stabilized, andthe power reduction of the output light is efficiently suppressed.

(3) since the relationship W2<W3 is further satisfied in addition to theabove-described relationship (W2<W1), it is possible to avoid reductionof transmissivity of the optical member that is disposed in theoptical-path, caused by the effect of an adhesive or a holding memberwhich holds the bottom side portion of the external resonator. It isthereby possible to further improve the light utilization efficiency.

In addition, the external resonator 313 needs to align the reflectionface of the external resonator 313 with the light source, based on thelength in the direction of a beam and reflection angle, while it is easyto fix the external resonator 313 and the light source at a desiredangle while easily aligning the external resonator 313 and the lightsource, and it is possible to prevent interception of the second laserlight LS2.

(4) Since it is possible to both make the light incident into theoptical-path conversion element 314 via the surfaces 315A and 316A ofthe prisms 315 and 316, respectively, and cause the tight to emit fromthe optical-path conversion element 314, it is possible to easilycontrol the direction of the light which is incident into theoptical-path conversion, element 314, and the direction of the lightwhich is emitted from the optical-path conversion element 314.

(5) Conventionally, there is a high possibility that the laser lightsource device 31 will be used in combination with other optical devicessuch as diffusion optical members, lenses, filters, mirrors, diffractiongratings, prisms, light modulation elements, and the like. However, thecharacteristics of these optical devices are variable depending on theangle of the incidence light and the output results.

Furthermore, illumination loss occurs for obtaining margin inirregularities of illumination region, caused by irregularities of theangles of the incidence light.

However, in the laser light source device 31 of this embodiment, sincethe second laser light LS2 is substantially parallel to the first laserlight LS1 emitted from the external resonator 313, it is thereby easy todesign an optical device or to determine the position of an opticaldevice, which is disposed behind the laser light source device 31.

Therefore, when the laser light source device 31 of this embodiment isapplied to an image display device, a monitor device, or the like, it ispossible to obtain effects where the degree of freedom in optical designincreases dramatically.

Furthermore, since the illumination region which is obtained in advanceof the diffusion optical member is formed on the region which isdepended on the incidence angle of the laser beam, it is possible toilluminate the substantially same region, and it is possible toilluminate a desired area with a high level of illumination efficiency.

Second Embodiment

FIG. 6 is a schematic view showing the constitution of a laser lightsource device of a second embodiment.

The laser light source device 41 of the second embodiment is differentfrom the laser light source device 31 of the first embodiment withregard to only the constitution of an optical-path conversion element414. The other elements are the same as the first embodiment.

Therefore, in FIG. 6, identical symbols are used for the elements whichare identical to those of the first embodiment and the explanationsthereof are omitted or simplified.

In addition, the process in which the output light is obtained from thelaser light source device 41 is also the same as in the first embodimentand the explanations thereof are omitted or simplified.

In the laser light source device 41, as shown in FIG. 6, an optical-pathconversion element 414 includes a platy member (not shown) which is atranslucent member, the selective reflection film 317, and a reflectionmirror 416.

The selective reflection film 317 is formed on a first surface of theplaty member, and the reflection mirror 416 is provided on a secondsurface of the platy member.

Similarly to the selective reflection film 317, the reflection mirror416 can be constituted by a dielectric multilayer.

Here, the dielectric multilayer constituting the reflection mirror 416may be a dielectric multilayer different from or the same as theselective reflection film 317.

Furthermore, the reflection mirror 416 may be constituted from a metalfilm such as aluminium, chrome, or argentum.

Generally, the dielectric multilayer has superior heat resistancecompared with the metal film.

The dielectric multilayer can improve reflectance relative to the lightof the specific wavelength by optimizing the thickness of each layerconstituting the dielectric multilayer, the material of each layer, andthe number of layers, and is also suitable to efficiently reflect lighthaving a high level of directivity whose wavelength-band is narrow likea laser.

In contrast, the metal film is more advantageous than the dielectricmultilayer with regard to the cost.

It is preferable that anti-reflective films (AR films) be formed on thesurfaces opposite to the surfaces on which the selective reflection film317 and the reflection mirror 416 are formed.

By forming the AR films on the surfaces, it is possible to decreaselight loss when the light is incident into the optical-path conversionelement 414 via the surfaces, or when light is emitted from theoptical-path conversion element 414 via the surfaces.

Next, the process in which output light is obtained from the laser lightsource device 41 will be described with reference to FIG. 6.

The light source 311 emits light of a first wavelength.

The light of the first wavelength emitted from the light source 311 isincident into the optical-path conversion element 414, passes throughthe selective reflection film 317, and is emitted toward the wavelengthconversion element 312.

That is, in the laser light source device 41 of this embodiment, a lightemission surface of the light source 311 is arranged so as tosubstantially face the AR film 312B of the wavelength conversion element312.

The light of the first wavelength emitted from the optical-pathconversion element 414 is incident into the wavelength conversionelement 312.

In the wavelength conversion element 312, a wavelength of a part of thelight of the first wavelength that has been incident is converted intolight half the wavelength (second wavelength) of the light.

In the light emitted from the wavelength conversion element 312, thelight that has been converted into the second wavelength passes throughthe external resonator 313, and is emitted from the external resonator313 as the first laser light LS1.

In contrast, in the light emitted from the wavelength conversion element312, the light (light of the first wavelength) that has not beenconverted into the second wavelength is reflected by the externalresonator 313 toward the light source 311.

The light of the first wavelength which has been reflected by theexternal resonator 313 re-passes through the wavelength conversionelement 312 in the process of traveling to the light source 311. Inaddition, a part of the light is converted into light of the secondwavelength.

The light emitted from the wavelength conversion element 312 toward thelight source 311 is incident into the selective reflection film 317.

In the light which has been incident into the selective reflection film317 in this manner, the light of the first wavelength passes through theselective reflection film 317.

The light of the first wavelength which has passed through the selectivereflection film 317 emitted from the optical-path conversion element 414toward the light source 311.

Furthermore, the light is returned to the light source 311, reflected bythe mirror layer formed therein, and re-emitted from the light source311.

As described above, the light of the first wavelength oscillates on thefirst optical-path O1 formed between the light source 311 and theexternal resonator 313. The light is thereby amplified by resonationwith the light newly oscillated in the laser medium 311B.

That is, the laser light source device 41 includes a resonator structureformed between the mirror layer inside the light source 311 and theexternal resonator 313.

In contrast, the light, which has been converted into light of thesecond wavelength by the wavelength conversion element 312 in theprocess of traveling to the light source 311 due to the reflection fromthe external resonator 313, is reflected by the selective reflectionfilm 317.

In addition, the light is reflected by a reflection mirror 416, therebyled in a direction substantially parallel to the direction of travel ofthe first laser light LS1, and emitted as the second laser light LS2.

According to the laser light source device 41 of this embodiment, it isalso possible to obtain the effects described below in addition to theabove-described effects (1), (2), and (4) to (6) of the firstembodiment.

It is possible to obtain the optical-path conversion element 414 whichis more lightweight than when a prism is used as a translucent member.

In addition, the platy member is more easily fabricated than the prism.

It is thereby possible to allow the laser light source device to belightweight and to reduce the cost.

Modified Example of Embodiment

The invention shall not be limited to the above-described first andsecond embodiments. As a matter of course, the invention may includevarious modifications of the embodiment in a scope not deviating fromthe spirit of this invention.

In the configuration described below as a modified example, it is alsopossible to obtain the same effects as the above-described embodiments.

Instead of the above-described surface emission-type semiconductorlaser, such as the light source 311, a laser light source such as anedge-emission-type laser or a solid laser excited by laser diodes can beused.

When using the edge-emission-type laser, it is preferable that a lenscausing the light emitted from the light source 311 to collimate bedisposed between the light source 311 and the optical-path conversionelements 314 and 414.

As the light source 311, a laser light source including a plurality ofarrayed emission sections may be used.

FIGS. 7A and 7B are schematic perspective views showing the light sourcein which emission sections are arrayed.

In the laser light source 321, as shown in FIG. 7A, a plurality ofemission sections 322 is arrayed in a line.

In the laser light source 323 as shown in FIG. 7B, a plurality ofemission sections 322 is also arrayed in two lines.

The number of emission sections and the number of lines of emissionsections are not limited to that shown in FIGS. 7A and 7B.

When the tight source including the arrayed emission sections is appliedto the above-described laser light source devices 31 and 41, the area ofthe emission end face (incidence end face) of the selective reflectionfilm, the reflection surface, the wavelength selective element, and theexternal resonator, is suitably extended as needed depending on the areaof the arrayed emission sections.

Therefore, in the above-described laser light source devices 31 and 41,even if the light source includes the arrayed emission sections, thelaser light source devices 31 and 41 do not need to be increased insize, and it is possible to utilize a simple constitution.

Therefore, in the above-described laser light source devices 31 and 41,even if the light source is an array, it is possible to efficientlyimprove the output power of the output light by increasing the amount oflight due to the arrayed light source, while obtaining the effects inwhich power reduction of the output light can be efficiently suppressed,light utilization efficiency can be improved, the output light has acompleted polarization direction, and the output can be stabilized.

In the above explanation, as the nonlinear optical material constitutingthe wavelength conversion element 312, materials such as LN (LiNbO₃) orLT (LiTaO₃) are used. As for the other materials constituting thewavelength conversion element 312, inorganic nonlinear optical materialsuch as KNbO₃, BNN (Ba₂NaNb₅O₁₅), KTP (KTiOPO₄), KTA (KTiOAsO₄), BBO(β-BaB₂O₄), LBO (LiB₃O₇), and the like can be used.

Furthermore, low-molecular organic material such as metanitroaniline,2-methyl-4-nitroaniline, chalcone, dicyanovinylanisole,3,5-dimethyl-1-(4-nitrophenyl)pyrazole, N-methoxymethyl-4-nitroaniline,the like, or organic nonlinear optical material such as poled polymer orthe like may be used.

As the wavelength conversion element 312, a Third Harmonic Generationelement may be used instead of the above-described SHG element.

As the external resonator 313, not only the above-described volume phasegrating, but also a crystal-type volume hologram, a Photopolymer volumehologram, a blazed diffraction grating (diffraction grating whose grooveis formed in a serration form in a cross-sectional view), or the likemay be used.

In the constitution of the above-described embodiment, the externalresonator 313 performs the wavelength-selection and causes the visiblelight to pass through. However, as shown in FIG. 8, the above-describedresonator may be constituted by in combination with a band-pass filterBP and a wide-band mirror M.

The band-pass filter BP is the filter which causes a wavelength or awavelength-band to pass through, and reflects the light having thewavelength shorter than the wavelength-band and the wavelength longerthan the wavelength-band.

Furthermore, as shown in FIG. 8, a transmission wavelength is adjustedby varying the incidence angle of the light, and thewavelength-selection is performed.

In this case, the wavelength-selection is performed by the band-passfilter BP, and the wide-band mirror M functions as the mirror throughwhich the visible light passes.

In this case, the height W3 of the external resonator as shown in FIG. 1corresponds to the width of the wide-band mirror M.

Illumination Device

As an illumination device of an embodiment of the invention, such as theconstitution of the illumination device 500 to which, for example, theabove-described laser light source device 41 is applied, will bedescribed below.

FIG. 9 is a schematic view showing a constitution of an illuminationdevice 500.

Illustrations are simplified in the FIG. 9, and the optical-pathconversion element 414 is omitted.

As shown in FIG. 9, the illumination device 500 includes the laser lightsource device 41, and a diffusion optical member 50 diffusing the lightemitted from the laser light source device 41 and uniformizing theillumination distribution of the laser light.

The diffusion optical member 50 is constituted by a hologram element.

As the hologram element, a computer generated hologram (CGH) may be usedon the basis of calculation using a calculator. The computer generatedhologram is formed with interference fringes, which are artificiallycreated on a hologram plate.

The computer generated hologram is suitable because a divided region ofa diffraction grating can be freely set, and aberration does nottherefore occur.

Generally, in the diffusion optical member 50 constituted by thecomputer generated hologram, irregularities are occurred caused by, forexample, errors in production or the like, clean so light may notthereby be obtained.

Such phenomenon will be specifically distinguished when the diffusionoptical member is enlarged.

A small sized diffusion optical member has a high level of image qualityof light, and can perform the irradiation with the clean light havinguniformized illumination distribution onto an object.

That is, reduction of the size of the diffusion optical member isdesired.

Therefore, since the illumination device 500 of this embodiment includesthe above-described laser light source device 41, the size of thediffusion optical member 14 can be reduced, and the image quality of thelight is enhanced.

Therefore, the illumination device which can illuminate a projectionobject with light having a clear and uniform illumination distribution,and which has high performance can be realized.

Image Display Device

As an image display device of an embodiment constitution of theprojector 3 to which the above-described laser light source device 31 ofthe first embodiment is applied, will be described below.

FIG. 10 is a schematic view showing the constitution of an opticalsystem of a projector 3.

In FIG. 10, the projector 3 includes the above-described illuminationdevice 500 which is the light source section, a liquid crystal panel 32(light modulation element) which is a light modulation device,polarization plates 331 and 332, a cross-dichroic prism 34, a projectionlens 35, and the like.

A liquid crystal light valve 33 is constituted by the liquid crystalpanel 32, the incidence polarization plate 331 disposed on the surfaceof liquid crystal panel 32 into which light is incident, and theemission polarization plate 332 disposed on the surface of liquidcrystal panel 32 from which the light is emitted.

The illumination device 500 is constituted by a red-colored light source500R emitting a red-colored laser light, a blue-colored light source500B emitting a blue-colored laser light, and a green-colored lightsource 500G emitting a green-colored laser light.

These light sources 500R, 500G, and 500B are disposed so as to each faceone of the three side surfaces of the cross-dichroic prism 34.

In the FIG. 10, the red-colored light source 500R and the blue-coloredlight source 500B are disposed so as to be on opposite sides of, andsandwiching the cross-dichroic prism 34. Also, the projection lens 35and the green-colored light source 500G are disposed so as to be onopposite sides of and sandwiching the cross-dichroic prism 34. Thesepositions are each changeable, as needed.

The liquid crystal panel 32 includes switching elements such as apoly-silicon TFT (Thin Film Transistor).

Each colored light emitted from the illumination device 500 is incidentinto the liquid crystal panel 32 via the incidence polarization plate331.

The light which has been incident into the liquid crystal panel 32 ismodulated depending on image information. The modulated light is therebyemitted from the liquid crystal panel 32.

Specified linearly polarized light in the light modulated by the liquidcrystal panel 32 passes through the emission polarization plate 332, andgoes toward the cross-dichroic prism 34.

The cross-dichroic prism 34 is the optical element synthesizing thecolored lights which have been modulated by liquid crystal panels 32 andforming a color image.

The cross cross-dichroic prism 34 is formed by connecting fourright-angle prisms. The cross-dichroic prism 34 is formed by pastingfour right-angle prisms, in a substantially regular square in a planview.

Two-type dielectric multi layers are formed in the shape of X on aboundary face of the prisms.

These dielectric multi layers reflect each colored light emitted fromthe liquid crystal panels 32 which are disposed so as to be oppositeeach other, and cause the light emitted from the liquid crystal panel 32disposed so as to be opposite the projection lens 35 to passtherethrough.

In this manner, each colored light that has been modulated in the liquidcrystal panel 32 is synthesized, and the color image is formed.

The projection lens 35 is constituted as an integrated lens combinedwith a plurality of lenses.

The projection lens 35 projects and enlarges the color image L.

According to the projector 3 of this embodiment, since the illuminationdevice including the above-described laser light source device, is usedas the light source section, a high level of light utilizationefficiency is obtained.

In this embodiment, the above-described illumination device 500 (500R,500G, 500B) are used. However, one or all of them may be substitutedwith the laser light source device 31 of the other embodiment or thelaser light source device of the above-described modified example.

In this embodiment, the example of projector including three lightmodulation elements is explained. However, the constitution described inthis embodiment can be applied to a projector including one, two, ormore man four light modulation devices.

Also, in this embodiment, the transmission-type projector is explained.The illumination device 500 or the laser light source devices 31 and 41constituting the illumination device can also be applied to areflection-type projector.

Here, the “transmission-type projector” means the projector includingthe tight modulation element through which the light passes. The“reflection-type projector” means the projector including the lightmodulation element in which the light reflects.

As the light modulation element, not only the liquid crystal panel 32,but also a device including, for example, a micromirror may be used.

Furthermore, as the projector, a front projection-type projector inwhich an image is projected onto a screen from the viewer side of thescreen, and a rear projection-type projector in which an image isprojected onto a screen from the opposite side of the viewer side of thescreen, are both well-known. The illumination device 500 or the laserlight source devices 31 and 41 constituting the illumination device canbe applied to both the front projection-type projector and the rearprojection-type projector.

Furthermore, in this embodiment, as an example of the image displaydevice including the illumination device 500, the projector thatincludes the projection lens 35 magnifying and projecting an image isintroduced, however, an image display device that does not include theprojection lens 35 can also be applied thereto. In addition, an imagedisplay device including the laser light source devices 31 and 41 of thefirst and second embodiment and the modified example thereof can also beapplied thereto.

In addition, the laser light source device of the invention can also beapplied to the image display device in which an image is displayed by ascanning section that scans an image onto a screen with the laser lightfrom the laser light source device.

Monitor Device

Finally, an example constitution of the monitor device 40 including theabove-described laser light source device 31, will be described below.

FIG. 11 is a schematic view showing a monitor device.

The monitor device 40 includes a main body 410 and a light transmissionsection 420.

The main body 410 includes the laser light source device 31 of the firstembodiment described above.

The light transmission section 420 includes a light guide 421transmitting light and a light guide 422 receiving light.

Each of the light guides 421 and 422 is constituted from a plurality ofoptical fibers that are sheaved. Therefore, it is possible to transmitthe laser light a distance.

The laser light source device 31 is disposed at the position which isclose to the incidence end face of the transmitting light guide 421. Adiffusing plate 423 is disposed at the position which is close to theemission end face of the transmitting light guide 421.

The laser light emitted from the laser light source device 31 istransmitted through the light guide 421 and the diffusing plate 423disposed at the end of the light transmission section 420, and isdiffused by the diffusing plate 423. Therefore, the laser lightilluminates an object.

Also, since an image-formation lens 424 is disposed at the end of thelight transmission section 420, the image-formation lens 424 can receivethe reflection light reflected by the object.

The received reflection light is transmitted through the receiving lightguide 422 and to a camera 411 which is an image capturing section formedin the main body 410.

As a result, due to the laser light emitted from the laser light sourcedevice 31, the object is illuminated, the reflection light reflected bythe object is obtained, and the image formed from the reflection lightcan be captured by the camera 411.

According to the monitor device 40 constituted as described above, sincethe laser light source device 31 can illuminate an object with the lighthaving a high level of light utilization efficiency, it is possible toimprove the brightness of the image captured by the camera 411.

In the monitor device 40 of this embodiment, the monitor device 40 usesthe laser light source device 31 of the first embodiment. However,instead of the laser light source device 31, the laser light sourcedevice 41 described in the other embodiments or the laser light sourcedevice of the modified examples may be used.

Furthermore, the illumination device, including the laser light sourcedevices 31 and 41 or the laser light source device of the modifiedexamples thereof, may be used.

Third Embodiment

FIGS. 12A and 12B are schematic views showing the constitution of alaser light source device 51 of a third embodiment. FIG. 12A is a sideview showing the laser light source device 51. FIG. 12B is across-sectional view illustrating the optical-path in the laser lightsource device 51.

The laser light source device 51 of the third embodiment includes asupport member 518 which supports an optical-path conversion element514, and which is an optical-path adjustment section. The other elementsare similar to the above-described first and second embodiments.

Therefore, in FIGS. 12A and 12B, identical symbols are used for theelements which are identical to those of the above-describedembodiments, and the explanations thereof are omitted or simplified.

In addition, the process in which output light is obtained from thelaser light source device 51 is also the same as the above-describedembodiments, and the explanations thereof are omitted or simplified.

The laser light source device 51, as shown in FIGS. 12A and 12B,includes first and second prisms 515 and 516 which are translucentmembers, and a selective reflection film 517 provided therebetween.

The first prism 515 and the second prism 516 are formed in an isoscelestriangular pillar-shaped form similar to each other, the low-angle isset to 45°.

The first prism 515, the second prism 516, and the selective reflectionfilm 517 are formed in one body by connecting.

The support member 518 is provided on a surface 515A of the first prism515.

The support member 518 adjusts the optical-path conversion element 514so that the first laser light LS1 is output from a predetermined height(position) of the wavelength conversion element 312.

Specifically, the support member 518 positions the position of theoptical-path conversion element 314 upper than the wavelength conversionelement 312.

That is, the support member 51 lifts up a surface 515C (reflectionsurface) of the first prism 515 which reflects the light from the lightsource 311, and can thereby lead the first laser light LS1 to be outputfrom the predetermined height H.

Here, the position of surface 515C which reflect the light of the lightsource 311 is P1.

Furthermore, the light, which has been converted into light of thesecond wavelength by the wavelength conversion element 312 in theprocess of traveling to the light source 311 due to the reflection fromthe external resonator 313, is reflected by the selective reflectionfilm 517.

Furthermore, the light of second wavelength which is the second laserlight LS2 is emitted due to reflection by a surface 516C of the secondprism 516.

Here, the position of the surface 516C which reflects the light of thesecond wavelength is P2.

Distances from a connection face P0 in the first prism 515 and thesecond prism 516 to the above-described P1 and P2 are set tosubstantially equal.

That is, the W2 (the optical-axes between the first laser light LS1 andthe second laser light LS2) can be expressed as (distance between P2 andP0) √{square root over (2)}.

Therefore, the W2 can be set to a desired value by optionally modifyingthe form of the above-described support member 518, and it is possibleto obtain the configuration in which the relationship W2<W1 issatisfied.

Furthermore, in this embodiment, as shown in FIG. 13, theabove-described support member 518 supports the optical-path conversionelement 514 so that a point of intersection X by extending thereflection surface (surfaces 516B and 516C) of the second prism 516substantially accords with the height of top surface of the wavelengthconversion element 312.

It is thereby possible to emit the first laser light LS1 and the secondlaser light LS2 toward the exterior where the laser lights are close toeach other.

Fourth Embodiment

FIG. 14 is a schematic view showing a constitution of a laser lightsource device 61 of a fourth embodiment.

The laser light source device 61 of the fourth embodiment includes asupport member 618 which supports an optical-path conversion element614, and which is an optical-path adjustment section.

Furthermore, in this embodiment, the optical-path conversion element 614is constituted by a quadrangle pillar-shaped prism 615.

The other elements are similar to the above-described third embodiment.

Therefore, in FIG. 14, identical symbols are used for the elements whichare identical to those of the above-described third embodiment, and theexplanations thereof are omitted or simplified.

In addition, the process in which output light is obtained from thelaser tight source device 61 is also the same as the third embodiments,and the explanations thereof can be omitted or simplified.

The quadrangle pillar-shaped prism 615 includes an optical-pathseparation surface 615A that reflects the light from the light source311 and that leads the tight which has been converted into the secondwavelength when the light is reflected by the external resonator 313 andpasses through the wavelength conversion element 312 to be transmitted.

The light of the second wavelength which is captured via theoptical-path separation surface 615A into the inner is reflected by areflection surface 615B which is disposed so as to face to theoptical-path separation surface 615A. After this reflection, the lightwhich is the second laser light LS2 is emitted from the above-describedoptical-path separation surface 615A toward the exterior.

The above-described support member 618 makes the angle between theabove-described optical-path separation surface 615A and the top surfaceof the wavelength conversion element 312 to be set at substantially 45°.

An end face PA of the optical-path separation surface 615A is disposedto be distant from the light source 311 further than the top surface ofthe wavelength conversion element 312.

Therefore, by including the above-described support member 618, thedevice configuration in which the relationship W2<W1 is satisfied can beobtained, and similar to the above-described embodiments, the laserlight source device 61 can be provided in which the first laser lightLS1 and the second laser light LS2 are extracted toward the exteriorwhere the laser lights are close to each other.

In addition, since the quadrangle pillar-shaped prism is used as theoptical-path conversion element 614, it is possible to lessen theboundary faces compared with when a plurality of prisms is combined (asin the first and second embodiment), and it is possible to decrease thelight loss.

Fifth Embodiment

FIG. 15 is a schematic view showing a constitution of a laser lightsource device 71 of a fifth embodiment.

The laser light source device 71 of the fifth embodiment includes asupport member 718 which supports an optical-path conversion element714, and which is an optical-path adjustment section.

In addition, in this embodiment, the optical-path conversion element 714is constituted by first and second mirrors 715 and 716. The otherelements are similar to the above-described fourth embodiment.

Therefore, in FIG. 15, identical symbols are used for the elements whichare identical to those of the above-described fourth embodiment, and theexplanations thereof are omitted or simplified.

In addition, the process in which output light is obtained from thelaser light source device 71 is also the same as the above-describedfourth embodiment, and the explanations thereof can be omitted orsimplified.

The first mirror 715 includes an optical-path separation surface 715Athat reflects the light of the light source 311 and that leads the lightwhich has been converted into the second wavelength when the light isreflected by the external resonator 313 and passes through thewavelength conversion element 312 to be transmitted.

The optical-path separation surface 715A is constituted by theabove-described selective reflection film 317.

Furthermore, the second mirror 716 reflects the light of the secondwavelength that has been passed through the optical-path separationsurface 715A.

The light of the second wavelength that has been reflected by the secondmirror 716 passes through the first mirror 715, and emitted toward theexterior, as the second laser light LS2.

Here, the above-described support member 718 can adjust the optical-pathof the light source 311 so that the first mirror 715 is set at apredetermined angle to the second mirror 716, and the first laser lightLS1 is output from the predetermined position of the wavelengthconversion element 312.

Therefore, the device configuration in which the relationship W2<W1 issatisfied can be obtained, and similar to the above-describedembodiments, the laser light source device 71 can be provided in whichthe first laser light LS1 and the second laser tight LS2 can beextracted toward the exterior in the state that the laser lights areclose to each other.

In addition, in this embodiment, since the mirror is used as theconstitution reflecting the light from the light source 311, the deviceconfiguration is simplified, and it is possible to realize the reductionof the cost in the laser light source device 71.

Modified Example

A modified example regarding the laser light source device is explainedbelow.

FIG. 16 is a schematic view showing a constitution of a laser lightsource device 41 of a modified example of the above-described secondembodiment.

As shown in FIG. 16, in this modified example, after the light of thelight source 311 is reflected by a reflection mirror 417, the light isled to be incident into the selective reflection film 317.

That is, the point including the reflection mirror 417 is different fromthe constitution of the above-described second embodiment.

Since the reflection mirror 417 is provided, the degree of freedom inposition at which the light source 311 is disposed can increase.

Furthermore, in the laser light source device 41 of the above-describedsecond embodiment and this embodiment a point of intersection X made byextending the reflection surface of the reflection mirror 416 and thereflection surface of the selective reflection film 317 cansubstantially accord with the height of top surface of the wavelengthconversion element 312.

Therefore, the configuration in which the first laser light LS1 and thesecond laser light LS2 are close to each other, that is, the deviceconfiguration in which the relationship W2<W1 is satisfied, can beacceptably obtained.

FIG. 17 is a schematic view showing a constitution of a laser lightsource device 51 of a modified example of the above-described thirdembodiment.

As shown in FIG. 17, in this modified example, the base section Bholding the light source 311, the wavelength conversion element 312, andthe external resonator 313 are sloped configuration.

In FIG. 17, an illustration of the support member supporting theoptical-path conversion element 814 is omitted.

The base member B includes the sloped configuration, and it is therebypossible to obtain the laser light source device emitting the first andsecond laser light LS1 and LS2 at the predetermined angle of elevation.

Furthermore, since the base member B includes the sloped configuration,a reflection light beam at an incidence face 815A of the first prism 815is not returned to the light source 311.

Therefore, the resonance caused by an unwanted light beam becoming anoise component can be suppressed, and it is possible to obtainefficient emission.

1. A laser light source device comprising: a light source emitting lightof a first wavelength; an external resonator selectively reflecting thelight of the first wavelength and thereby leading the light toward thelight source, and emitting a first laser light of a second wavelengthwhich is different from the first wavelength; a wavelength conversionelement provided in a first optical-path formed between the light sourceand the external resonator, and converting the wavelength of part ofincident light having the first wavelength into the second wavelengthwhich is different from the first wavelength; and an optical-pathconversion element causing the light that has been converted into lightof the second wavelength in the process of traveling to the light sourcedue to reflection from the external resonator to be separated into asecond optical-path different from the first optical-path, and emittinga second laser light of the second wavelength, wherein the first laserlight and the second laser light are utilized as output lights, and theheight of the wavelength conversion element is greater than a distancebetween an optical-axis of the first laser light on an end face of thewavelength conversion element which is close to the external resonatorand an optical-axis of the second laser light.
 2. The laser light sourcedevice according to claim 1, wherein the height of the externalresonator is greater than the distance between the optical-axis of thefirst laser light and the optical-axis of the second laser light.
 3. Thelaser light source device according to claim 1, wherein the first laserlight is substantially parallel to the second laser light.
 4. The laserlight source device according to claim 1, wherein the length of theoptical-path conversion element in the direction of the beam of thesecond laser light emitted from the optical-path conversion element isshorter than the height of the optical-path conversion element.
 5. Alaser light source device comprising: a light source emitting light of afirst wavelength; an external resonator selectively reflecting the lightof the first wavelength and thereby leading the light toward the lightsource, and emitting a first laser light of a second wavelength which isdifferent from the first wavelength; a wavelength conversion elementprovided in a first optical-path formed between the light source and theexternal resonator, converting the wavelength of part of incident lighthaving the first wavelength into the second wavelength which isdifferent from the first wavelength, and thereby obtaining harmonics; anoptical-path conversion element causing the light that has beenconverted into light of the second wavelength in the process oftraveling to the light source due to reflection from the externalresonator to be separated into a second optical-path different from thefirst optical-path, and emitting a second laser light of the secondwavelength; and an optical-path adjustment section adjusting the firstlaser light to be output from a predetermined position in the wavelengthconversion element, wherein the first laser light and the second laserlight are utilized as output lights.
 6. The laser light source deviceaccording to claim 5, wherein the optical-path conversion elementincludes: a fundamental-wave conversion section converting theoptical-path of the light of the first wavelength from the light source;a separation section selectively reflecting the light that has beenconverted into the second wavelength in the process of traveling to thelight source due to reflection from the external resonator and therebyseparating the light into the second optical-path; and a harmonicsoptical-path conversion section converting the optical-path of light ofthe second wavelength that has been separated by the separation sectionand thereby making the light become the second laser light.
 7. The laserlight source device according to claim 5, wherein the optical-pathconversion element includes the optical-path adjustment section.
 8. Thelaser light source device according to claim 5, wherein the optical-pathadjustment section is constituted by a support member supporting theoptical-path conversion element.
 9. The laser light source deviceaccording to claim 1, wherein the wavelength conversion element includesa holding face onto which a face of the wavelength conversion element isheld, and a center section parallel to the optical-path of the firstlaser light in the wavelength conversion element, wherein theoptical-path of the first laser light is positioned inside thewavelength conversion element and between the center section and theoptical-path of the second laser light.
 10. The laser light sourcedevice according to claim 1, wherein the light source includes aplurality of arrayed emission sections.
 11. The laser light sourcedevice according to claim 1, wherein the wavelength conversion elementis a wavelength conversion element of Quasi Phase Matching.
 12. Anillumination device comprising: the laser light source device accordingto claim 1; and a diffusion optical member arranged in the direction oftravel of the laser light emitted from the laser light source device.13. The illumination device according to claim 12, wherein the diffusionoptical member is formed by a computer generated hologram.
 14. An imagedisplay device comprising: a light source section constituted by theillumination device according to claim 12; and a light modulationelement modulating the light emitted from the light source in accordancewith image information.
 15. A monitor device comprising: the laser lightsource device according to claim 1; a capturing section capturing anobject which is irradiated by the laser light source device.
 16. Thelaser light source device according to claim 5, wherein the wavelengthconversion element includes a holding face onto which a face of thewavelength conversion element is held, and a center section parallel tothe optical-path of the first laser light in the wavelength conversionelement, wherein the optical-path of the first laser light is positionedinside the wavelength conversion element and between the center sectionand the optical-path of the second laser light.
 17. The laser tightsource device according to claim 5, wherein the light source includes aplurality of arrayed emission sections.
 18. The laser light sourcedevice according to claim 5, wherein the wavelength conversion elementis a wavelength conversion element of Quasi Phase Matching.
 19. Anillumination device comprising: the laser light source device accordingto claim 5; and a diffusion optical member arranged in the direction oftravel of the laser light emitted from the laser light source device.20. An image display device comprising: a light source sectionconstituted by the illumination device according to claim 19; and alight modulation element modulating the light emitted from the lightsource in accordance with image information.